They look like they will do the job and can suppress weeds you could even use them to cover an area and cut holes for the plants you already have. Just remember these options are a very quick solution and should not be used long term, the plastic is an impermeable layer that will not allow for water to pass through. It will also keep way the air from the soil, microorganisms in the soil need both air and water to thrive. Killing off microorganisms will rapidly decrease the quality of the soil for future planting. You want a weed free area but not at the expense of your soil.
Bin bags are exceptionally light weight and can easily fly away if not securely pinned down. The bags are also not made for this purpose and are susceptible to UVA rays and will very quickly degrade, also taking in to account adverse weather this makes for an unsightly mess. Bin bags also easily rip if stepped on and this may allow weeds to push through any gaps once laid.
Basically get yourself some geotextile membrane whether non-woven or woven Give us a call at Spudulica home and garden to get the right one for you – 1051 515 1415